Magnetic chuck.



H. K. SPENCER.

MAGNETIC CHUCK.

APPLICATION FILED JAN.31, 191s.

Patented Jan. 19, 1915.

2 SHEETS-SHEET 1.

mineeses I nven/Z'or. M d Hen/119K (S ren/oer. da /ye xfiz M XW 7 H. K. SPENCER.

MAGNETIC CHUCK.

APPLICATION FILED mum. ms.

Patented Jan. 19, 1915 2 SHEETS-SHEET 2.

IfiJvenZo r ILI II Ill Plain/eases.-

CHUSETTS.

MAGNETIC CHUCK.

Application filed January 31, 1913.

To all whom it may concern: I

Be it known that I, HENRY K. SPENCER, a'

citizen of the United States, and a resident of Boston, county of Suffolk, and State of Massachusetts, (whose post-office address is 21 Nottingham street, Dorchester, Massachusetts,) have invented an Improvement in Magnetic Chucks, of which the following description, in connection with the accompanying drawings, is a specification, like characters on the drawings representing like )arts. 1 This invention relates to magnetic holding devices, and more especially, though not exclusively, to magnetic chucks intended for holding small pieces of magnetic material, while such pieces are being worked upon.

My invention will be best understood by reference to the following specification,- when taken in connection with the accompanying drawings, showing three illustrative embodiments, while its scope will be more particularly pointed out in the appended claims.

In the drawings: Figure l is a plan, partly in section, of one specific form of magnetic chuck embodying my invention; Fig. 2 is a sectional view of the chuck on line 2-2 of Fig. 1; Fig. 3 is a plan, partly in section, of another form of magnetic chuck embodying my invention; Fig. 4 is a sectional view on line 44 of Fig. 3; Fig. 5 is a sectional view on line 55 of Fig. 3; and Fig. 6 is a sectional view of still another form of magnetic chuck embodying my invention.

Referring first to Figs. 41 and 2 of the drawings, and to the embodiment of my invention which I have there shown for illustrative purposes, 7 is a work support formed of steel or other suitable magnetic material, and provided with a plurailty of annular concentric chambers, herein four in number, designated by the numerals 8, 9, 10 and 11. Located in these chambers, are suitable magnetizing coils 12, 13, 14 and 15, respectively.

It will be observed that the work support provides a continuous steel shell, without joints, above the coil chambers, and hence the coils are protected from the entrance of water. This is a matter of great practical advantage where it is desirable to flood the pieces of work onthe Work support with water, while the work is being per- Specification of Letters Patent.

concentric alternate poles Patented J an. 19, 1915. Serial No. 145,402.

formed, as,

for example, chine. The

bottoms of the coil chambers are preferably closed by a plate 16, formed .or. magnetic material, as for example, steel,

and secured to the work support by suitable means, herein severalsets .of screws 17 18, 19, 20 and 21.

Currents of equal magnitude are passed through alternate coils in opposite dire c}.

tions, that is to say, currents pass through the coils 12 and 14 in one direction, and through the coils l3 and 15 in the opposite direction, as indicated, for example, by arrows on the coils in Fig.1. This creates of opposite p0- larity, thus causing a magnetic circuit to flow around each'coil, the direction of the lines'of force being represented by dotted lines and arrows in Fig. 2. In order to provide for holding very small work pieces,

have made provision for sub-dividing each pole piece, thus providing a plurality of pole pieces within the compass of a given cross-section of the coil.

In the present embodiment, instead of separating unlike poles by non-magnetic separators adjacent the work face of the chuck, as heretofore, the work .support extends from pole to pole, and the magnetic circuit is complete without the inclusion of the pieces of the work. The latter are attracted and held by making suitable provision for diverting a part of the lines of force from their metallic circuit, and compelling them to fiow through the pieces of work to be held. While this result may be accomplished in other duced by narrowing the path of the magnetic circuit adjacent the work surface of the chuck, as for example, by providing the work support with a series of closely-spaced concentric grooves, which may be, and preferably are, filled with rings of suitable nonmagnetic material as, for example, brass, these rings being designated by the numerals 22 to 33, inclusive. It will be understood that these rings may be altogether omitted, if desired, in which case, t'he grooves will form air gaps performing the same function as the rings. The spacing between the bottoms of these rings, or grooves, and the tops of the coil chambers is less than the spacing between each coil chamber and the adjacent coil chamberon a .grinding maways, it is herein prowhile the spacing between each ring, or groove, and the adjacent ring, or groove, is greater than the space between the bottoms of the rings andthe tops ofthe Hence, when pieces of magnetic work, as for example the work pieces 34, 35, 36, and 37-, are laid upon the work support surface, since the efiective cross section of the magnetic circuit between the bottoms of the 1 rings and the tops of the coil chambers is reduced, as described, the greater part of the magnetic flux will be compelled to flow between the rings and into and through the pieces of work, as represented by dotted lines in Fig. 2. It must now be evident that by utilizing the described construction, am enabled to provide a magnetic holding device whose holding points are much more closely spaced than is possible in chucks of the type in' 'which there is an actual separation of the. poles, this being so because of the practical minimum limit of size of the magnetizing coils. By the described construction, I am enabled to provide a chuck which will hold very thin pieces of work, as exemplified by the piece 34, and very small pieces of work, as exemplified by the pieces 35, 36 and 37, which could not be held, except at a limited number of points, on a chuck having more widely spaced holes. In the present type of chuck, therefore, the entire area is available for small pieces of work.

The chuck proper may be mounted in any suitable manner, but herein is secured to a driving gear 38, on which two metallic'contact rings 39 and 40 are mounted, the latter being insulated from the gear by a ring 41 of insulating material. The contact rings 39 and 40, which in practice will be suitably connected to the magnetizing coils, cooperate with fixed brushes 42 and 43, which will be connected in circuit with a suitable source of current, not shown.

It will be understood that the features 4 just described, relating to the mounting of the chuck, form no essential part of my present invention, and may be suitably varied as the circumstances require.

Referring now to Figs. 3, 4 and 5, wherein I have shown another form of chuck em-a bodying my invention: In this form, the principle involved is the same as that in the form first described, but is applied to a rectangular chuck having a work support 44.

This work support is provided with ,a chamber 45, and has a plurality of walls, herein four designated by the numerals 46, 47, 48, and 49, about which are placed suitable magnetizing coils 50, 51, 52 and 53, respectively, within the coil chamber. The bottom of the coil chamber is preferably closed by a plate 54, of steel or other suitable magnetic material, secured to the work holder by suitable means as, for example,

chambers.

.magnetic circuits of the grooves and the tops of the scribed, the differences being rality of screws 55, 56,57, 58, 59 and 60. The sides of the chamber 45 may be closed by suitable plates 61-61..

The magnetizing coils will be supplied with currents of equal magnitude, the direction of the current in each coil being opposite to that of the current in the next adjacent coil, as indicated, for example, by the arrows on the coils in Fig. 3. sage of the current through the coils in this manner will set up in the magnetic mass arrows in Fig. 4. As a means for diverting a part of the lines of force from their natural magnetic circuit, and compelling such diverted lines to flow through the body held by the chuck, the port 44 may be provided with a series of transverse grooves, which may be, and preferably are, filled with strips of non-magnetic material, such as brass, these strips being designated by the numerals 62 to 7 6, inclusive. It will be understood, however, these strips may be altogether omitted 1 desired, in which case, the grooves will form air gaps performing the same function as the non-magnetic strips. In this form of my invention, as in the form first described, the grooves, or strips, are of such depth that they reduce the effective cross-sectional area of the magnetic mass between the bottoms chamber between these two points being less than the thickness of the walls 46, 47, 48 and 49. The space between each groove, or strip, and the next adjacent groove, or strip, however, is preferably greater than the distance between the bottoms of the grooves and the tops of the chamber, and hence the greater part of the mag- The pasmagnetic work supflowing about the respective coils, as represented by dotted lines and that f netic flux will be compelled to pass between the grooves or, strips, and into and through the pieces of work upon ing surface. The construction and operation of this form of my invention, and the advantages secured thereby, are essentially the same as those of the form first dechiefiy in the shape of the chuck.

Referring now to Fig. 6, wherein I have shown another form of. magnetic chuck embodying my invention: In this form I have shown an attachment capable of being applied to a common form of magnetic chuck, so as to secure the advantages of the forms already described.

In Fig. 6, the numeral 77 designates generally a magnetic chuck of common form, comprising a series of magnetic rings 78, 79, 80, 81 and 82, alternating with interposed non-magnetic rings 83, 84, 85 and 86, and forming annular chambers 87, 88, 89 and 90, in which magnetizing coils 91. 92, 93 and 94, are disposed; Preferably,

the work support- 15 been stated, the space between the the bottoms of the chambers are closed by a magnetic plate 95, secured to the magnetic rings by several sets of screws 96, 97, 98, 99 and 100. 1

Currents of equal magnitude are passed through the magnetizing coils, the direction of the current in each coil being opposite to that of the current in the next adjacent coil, and operating in a familiar manner to set up lines of force which Will flow from one magnetic ring to the next, provided, however, that there is a magnetizable body placed upon the upper surface of the chuck. In this form of chuck, however, as has already poles is necessarily so great as to preclude the holding of very small or thin pieces of work. Therefore, as a means for adapting this chuck to very small, or very thin, pieces of work, I have provided an attachment in the form of a work-supporting'- plate 101, secured to the chuck 77 in any suitablemanner, as by means of bolts 102 and screws 103. This work-supporting plate is provided with annular chambers 10%, 105, 106 and 107, corresponding to, and disposed above, the nonmagnetic rings 88, 84, 85, and 86, respecthese chambers are separated irom one another by annular magnetic walls 108, 109 and 110, corresponding to, and disposed above the magnetic rings 79, 80, and 81, respectively. The chambers 101, 105, 106 and 107, may be, and preferably are, filled with some suitable non-magnetic ma- 35 terial, as, for example, Babbitt metal, in the form of rings 111, 112, 113 and'llel. In this form of chuck, as in the forms already force to pass into the body held, the principle and mode of operation being precisely the same as in the forms already described.

While I have herein shown and described three specific embodiments of my invention 65 for illustrative purposes, and have disclosed and discussed in detail the construction and arrangement incidental to three specific applications thereof, it is to be understood that the invention is limited neither to the mere details nor relative arrangements of parts nor to its specific embodinu-nts heroin but that extensive deviations from the illustrated forms or embodiments of the invention may be made, without departing from the principles thereof as defined by the appended claims.

aving thus described my invention, what I claim and desire by Letters Patent to procure is: g

1. A magnetic holding device having, in combination, means for producing lines of magnetic force, means forming an uninterrupted circuit of magnetic material, said means having provision for causing a part of the lines of force to pass from said mag netic material and compelling such flow through the body held.

magnetic holding device having, in combination, a magnetizing coil, a work support consisting of a body of magnetic material forming a magnetic circuit within the support, and means to cause a portion of the magnetic flux to pass through a work piece on the support.

lines to A magnetic holding device having, in e combination, a magnetizing coil, a body of magnetic material forming a magnetic circuit, and means to reduce the effective crosssectional area of the magnetic mass at a portion of said circuit, thereby to compel a portion of the lines of force ,to pass into the body held.

4. A magnetic holding device having, in combination, a magnetizing coil, a body of magnetic material provided with a recess for said coil and provlding a complete magnetic circuit about the latter, and a series of non magnetic members extending part way only into the magnetic circuit thereby to divert some of the lines of force through the body held.

5. A magnetic holding device having, in combination, a magnetizing coil, an uninterrupted body of magnetic material adjacent said coil, and a plurality of non-magnetic members'embedded in but extending part way only through said body.

6. A magnetic holding device having, in combination, a magnetic massprovided with a recess, a magnetizing coil disposed in said recess, said mass forming a continuous path outside, of said path and through the work.

bedded in said magnetic mass, the spacing combination,

fie

I reduce combination,

A0 face provi between said non-magnetic means being greater than the space between said nonmagnetic means and said recess.

8. A magn'etic'holding device having, in a magnetic mass provided with a recess bounded on all sides but one with a magnetizable wall having a certain efiective cross-section, a magnetizing coil disposed in said recess, and spaced non-magnetic means 1) embedded in said magnetic mass on the remaining side of said recess and reducing the /effective cross-section of the remaining side to less than the efiective cross-section of the said wall. Y' 9. A magnetic holding device having, in, combination, a magnetizing coil or coils, and a magnetic body comprising a'pole piece or pieces adjacent the coils, said magnetic body being pro ided with a plurality. of grooves v 2-0 so disposed between the poles as to facilitate the flow of the magnetic lines of force through thebody to be held and cause the lines of force to enter and leave the body at a multiplicity of points.

25 10. A magnetic holding device having, in combination, a magnetizing coil, and a body of magnetic material forming a magnetic circuit, said. body having a wor -supporting face provided with a plurality of recesses to the effective cross-sectional area 0 the magnetic mass at a portion of said magnetic circuit, thereby to compel a portion 0 the lines of force to pass into the body held.

11. A magnetic holding device having, in

a magnetizing coil, and a body of magnetic material provided with a recess for said coil and providing a complete magnetic circuit of magnetic material about the latter, said body having a wor supporting ed with a plurality of recesses extending part way only into said magnetic material thereby to divert a part of the lines" of force through the body held.

12. A magnetic holding device having,- in

combination, a' magnetizing coil, and an uninterrupted body of magnetic material ladjacent said coil, said body being provided with a plurality of recesses extending part way only through said body.

13. A magnetic holding device having, in combination, a magnetic mass provided with a recess and a magnetizing coil disposed in said recess, said mass forming a continuous path 'for the magnetic circuit, and, having a recess or recesses to narrow the path at a part of said circuit thereby to compel a part of the lines of r'orce to pass outside said path and through th e work. p

14. A magnetic holding device having, in combination, a magnetic mass provided with a recess, and a magnetizing coil, isposed in said recess, said mass being provided with a plurality of spaced recesses, the spaces between the last-mentioned recesses being greater than the space between the last mentioned recesses and the first-mentioned. recess. i

15.' A magnetic holding device having, in\ combination, a magnetic mass provided with 70 a recess bounded on all sides but one with a magnetizing wall having a certain effective cross-section, and .a magnetizable coil disposed in said recess, said mass being provided on the remaining side of said recess with a plurality reducingthe eflfective cross-section of the remaining side to less than the eiiective crosssection of the said wall.

16. A magnetic holding device comprising, in combination, a pole piece, a magnetizing coil or coils having cross-sections in which currents flow in opposite directions at opposite sides of said pole piece, and a wor support comprising a series of separated magnetic-portions, there being a plurality of such magnetic portions within the width of each said cross-section.

In testimony whereof, I have signed 'my name to this specification, in the presence of 90 two su scribing witnesses.- 1

HENRY K. SPENCER.

Witnesses:

' LOUIS A. Jones,

CLARA LISTUART. 

